The present invention relates to batteries and, more particularly, to rechargeable modular battery packs for use with portable two-way radios.
Portable two-way radios and similar devices are typically powered by rechargeable batteries, such as nickel-cadmium battery cells packaged in a battery pack which is easily removable from the radio for recharging in a battery charger. The size of the battery pack and the number of cells vary, depending on the power and operational life of the battery required between chargings.
It is necessary on portable radios that means be provided for switching off battery power when the radio is not used in order to conserve battery life. It is also desirable to be able to operate the radio in a battery charger circuit, even if the battery is dead or defective, as a back-up mode of operation. Thus, an uncharged or defective battery should not cause loss of communications as long as a battery charger is available. This is referred to as dead battery operation. It is also desirable to be able to electrically isolate the battery terminals when the battery pack is being disconnected from the radio to prevent arcing. This is particularly desirable in the presence of explosive gases which could be ignited by such arcing.
Prior art radios confine the on-off switch to the radio body itself. This location requires that an electrical conductor be routed from the radio's battery contacts to the switch, and thereafter to a radio systems connection and/or distribution point. Generally, the size of the electrical conductor is relatively large in order to keep the electrical losses to a minimum. This presents several problems in a portable hand-held radio. First, a large electrical conductor takes up substantial space in an already crowded portable radio. Second, routing the electrical conductor through the systems portion of the radio usually results in a loss of accessibility to electrical components also located in that area.
Dead battery operation in prior art radios has been provided by means of switching contacts in the radio or isolation diodes in the battery, radio or charger circuits. These components add complexity and/or expense.